1. Field of the Invention
The present invention relates to a compound AC generator and, more particularly, to a compound AC generator having a control circuit so designed as to prevent the voltage pulsation in a shunt field winding from affecting a series field winding.
2. Description of the Prior Art
In general, a compound AC generator requires arrangement of its series field winding to have (1) a large diameter of the wire, (2) a large number of turns, and (3) to be divided into parallel circuits, in order to enhance the compensation for drooping of the terminal voltage of the generator due to overload. When using such a series field winding, however, the space occupied by the series field winding is larger than that of the shunt field winding, resulting in necessity of disposing the series and shunt field windings on a common magnetic pole. The series field winding is wound to be distributed uniformly on magnetic poles in order to reduce the resistance of the field winding, to reduce the heat evolved and to prevent nonuniform magnetic flux distribution. The shunt field winding is connected through a half-wave rectifier to the generator to receive a half-wave rectified field current and a flywheel diode is connected in parallel to the shunt field winding to prevent interruption of the field current during another half-cycle, whereby the shunt field winding is supplied with a pulsating field current without interruption, resulting in pulsating magnetic flux produced by the shunt field winding. This causes an exciting current to flow in a direction to increase the magnetic fluxes through the series field winding wound on the same magnetic pole in layers with the shunt field winding, resulting in variation of the output voltage of the generator. The effects of the variation of the output voltage is especially great at a light load and its voltage regulation is about 15%, thereby presenting poor performance as a power source.